Ziegler-Natta type catalysts for polymerization of unsaturated hydrocarbons, such as alpha olefins, have long been the state of the art catalysts for such reactions. Typically, Ziegler-Natta type catalysts are composed of transition metal salts and aluminum alkyl compounds, e.g., titanium tetrachloride and triethylaluminum. While these catalysts are very effective and have a long-established record of use, they are not without drawbacks. For example, transition metals are expensive, potentially present some toxicity hazards, and to some are environmentally objectionable. Therefore, efforts towards the development of alternative, suitable olefin polymerization catalysts have occurred. For example, metallocene catalysts have been developed for use in alpha olefin polymerization. The polymerization of ethylene using an aluminum-based catalyst but in the absence of a transition metal is known. For example, the formation of polyethylene by the polymerization of ethylene in the presence of catalysts prepared by the reaction of neutral aluminum compounds, such as Cl.sub.2 AlCH(Me)AlCl.sub.2 or (AlR.sub.3).sub.2, with ethylene at a temperature in the range of 25 to 50.degree. C. has been reported by H. Martin and H. Bretinger, Makromol. Chem. 1992, 193, 1283. However, the reported catalytic activities are very low (1.6.times.10.sup.-1 -3.8.times.10.sup.-4 g PE/ (mol*h*atm)).
The present invention has as its primary objective the development of more highly active catalysts useful for the polymerization of unsaturated hydrocarbons which do not require a transition metal compound as a component of the catalyst.
Another objective of the present invention is to prepare such catalysts in high yields using convenient and practical synthetic methods.
A yet further objective of the present invention is a method for polymerizing unsaturated hydrocarbons using the novel, transition metal-free catalysts provided by this invention.
The method and manner of accomplishing each of the above objectives, as well as others, will become apparent from the detailed description of the invention which follows hereinafter.